We have a family in which the proband has type 1 hyperoxaluria caused by previously unidentified mutations in the gene encoding alanine/glyoxalate aminotransferase. Sequencing maternal & paternal DNA reveals both parents to have presumably balanced hemizygous mutations in the AGAT gene. Since donating a kidney to her daughter, the mother now has hyperoxaluria. We will biopsy livers of both parents to establish functional correlates and to extract RNA for cDNA synthesis to sequence mutations in hepatic ATAT mRNA.